The present invention relates generally to pneumatic actuation control systems and methods and, more particularly, relates to systems and methods of pneumatically actuating a pressurizable object having a contained volume utilizing both a positive pressure and a negative pressure to provide fluid to, and draw fluid from, the contained volume.
Pneumatically actuated switching assemblies are commonly used in many industries, including the aircraft industry, to control pressurizable objects that include a contained volume. In this regard, where the pressurizable objects comprise mechanical displacement devices, such as inflatable bladders, pneumatically actuated switching assemblies generally include inflation-actuated switching assemblies and vacuum-actuated switching assemblies. An inflation-actuated switching assembly controls pressure within a contained volume by providing fluid, such as air, to the contained volume at a pressure greater than the pressure of fluid external to the contained volume. As such, the inflation-actuated switching assembly is capable of positively displacing, or inflating, the mechanical displacement device. In contrast, a vacuum-actuated switching assembly draws fluid from the contained volume by applying negative pressure (i.e., vacuum) to fluid within the contained volume. Thus, the vacuum-actuated switching assembly is capable of negatively displacing, or deflating, the mechanical displacement device.
Whereas inflation-actuated or vacuum-actuated switching assemblies are generally adequate for many applications, such switching assemblies have drawbacks. In particular, inflation-actuated and vacuum-actuated switching assemblies are generally designed for a single external pressure, such as sea level static atmospheric pressure. As such, in applications such as in aircraft, missiles and spacecraft that typically operate at multiple altitudes and, thus multiple atmospheric pressures, conventional inflation-actuated and vacuum-actuated switching assemblies do not continuously function properly across the range of encountered external pressures. In this regard, conventional inflation-actuated and vacuum-actuated switching assemblies cannot compensate for changes in altitude and, thus, changes in atmospheric pressure. Additionally, the rate of change in pressure can be very rapid for high performance platforms that climb and descend quickly.
In light of the foregoing background, embodiments of the present invention provide an improved pneumatic actuation control system and method for controlling a pressurizable object that defines a contained volume. Advantageously, the system and method of the present invention utilize both positive and negative pressure to control the pressurizable object and, additionally, compensate for changes in pressure external to the contained volume. Thus, the system and method can be used in applications that necessarily include changes in external pressure, such as changes in atmospheric pressure caused by increasing or decreasing the altitude of the pressurizable object. Also, the system and method of the present invention is capable of controlling the pressurizable object based upon highly sensitive measurements of pressure within, and external to, the pressurizable object. As such, the system and method of the present invention provide precision control of the pressurizable object that allows the system and method to operate in environments where the pressurizable object may encounter rapid changes in external pressure, such as changes due to rapid altitude changes.
According to one embodiment, a pneumatic actuation control system includes a pressure controller, an eductor and a valve. The pressure controller is capable of directing fluid flow, such as from a fluid source. In this regard, the pressure controller is capable of directing an amount of fluid to the contained volume such that a pressure of fluid within the contained volume exceeds a pressure of fluid external to the contained volume by a predefined positive pressure, such as a pressure approximately equal to or not exceeding 0.1 psi. The pressure controller is also capable of adjusting the pressure of fluid within the contained volume, such as by either providing additional fluid to the contained volume or drawing fluid from the contained volume, when the pressure external to the contained volume changes. As such, the pressure controller can be capable of measuring a pressure of fluid within the contained volume relative to a pressure of fluid external to the contained volume.
The eductor, on the other hand, is capable of drawing fluid from within the contained volume to thereby decrease the pressure of fluid within the contained volume. The valve, which is in fluid communication with the pressure controller, the eductor and the pressurizable object, is controllably operable in either a pressure mode or a vacuum mode. In pressure mode, the valve permits the pressure controller to either direct an amount of fluid to the contained volume or adjust the pressure within the contained volume. In vacuum mode, the valve permits the eductor to draw fluid from the contained volume. To control operation of the valve and, thus, the flow of fluid into and out of the contained volume, the system can also include a valve control switch capable of controlling operation of the valve.
According to the present invention, the pressure controller is capable of adjusting the fluid provided to the contained volume when the pressure of fluid external to the contained volume changes. In this regard, the pressure controller can be capable of repeatedly measuring the pressure of fluid within the contained volume relative to a pressure of fluid external to the contained volume. Thus, when the pressure of fluid external to the contained volume increases, the pressure controller is capable of providing additional fluid to the contained volume to thereby increase the pressure of fluid within the contained volume. For example, when the pressure of fluid external to the contained volume increases by an amount, the pressure controller is capable of providing additional fluid to the contained volume to thereby increase the pressure of fluid within the contained volume by the same amount. In contrast, when the pressure of fluid external to the contained volume decreases, the pressure controller is capable of drawing an amount of fluid from the contained volume to thereby decrease the pressure of fluid within the contained volume. Thus, for example, when the pressure of fluid external to the contained volume decreases by an amount said pressure controller is capable of drawing an amount of fluid from the contained volume to thereby decrease the pressure of fluid within the contained volume by the same amount.
In embodiments including a fluid source, the system can include a pressure regulator capable of regulating a pressure of fluid from the fluid source. In this regard, the pressure regulator is disposed between the fluid source and the pressure controller and in fluid communication with the fluid source and the pressure controller. Also, the pressure regulator is disposed between the fluid source and the eductor and in fluid communication with the fluid source and the eductor. A method of pneumatically actuating a pressurizable object that defines a contained volume is also provided.